1. Field of the Invention
The present invention generally relates to power supply units for electronic and computing systems, and more particularly to a system level power source integration to support handheld devices, computer systems, and other electronic equipment
2. Description of the Related Art
In today's wireless systems and personal systems continuous supply of power to maintain the quality of service becomes a major challenge. Using a battery to support the system usage becomes the primary operation mode in those systems. Although there are many new developments in the battery technology for longer usage period, lifetime, and operating environment, the integration of a battery into a system is proving to be bulky and inconvenient.
Currently, a battery management system is provided for very complex electrical and electronic-based circuits or devices, such as laptop computers, which typically utilize rechargeable batteries. In these applications, the battery management system typically provides a specialized serial interface, such as the SMBus, for interfacing with an external controller such as a micro-controller. These battery management systems consist of specialized circuitry which is optimized for the unique chemistry of the specific battery type being monitored and controlled (i.e., nickel cadmium, lithium, etc.).
A number of advanced battery technologies have recently been developed, such as metal hydride (e.g., Ni-MH), lithium-ion, and lithium polymer cell technologies, which would appear to provide the requisite level of energy production and safety margins for many commercial and consumer applications. However, such advanced battery technologies often exhibit characteristics that provide challenges for the designers and manufacturers of advanced energy storage devices.
Moreover, in recent years, there has been accelerated development of down-sized and cordless design schemes in the field of electronics apparatus or equipment. In view of this trend, batteries and battery systems are of increasing interest since these have increased applicability as the power supply for such electronic equipment due to their capability of size reduction and high electrical energy density.
These battery management systems and the associated microcontroller utilize current or voltage level monitoring techniques to switch between battery sources and/or to shut down the device being powered at a battery discharge level that is controlled by data stored in the memory. As such, current battery management systems are vastly complex and cost significantly greater than what can be justified for cheaper devices.
Additionally, the demand for new and improved electronic and electro-mechanical systems have placed increased pressure on the designers and manufacturers of energy storage devices to develop battery technologies that provide for high energy generation in a low-volume package. Conventional battery systems, such as those that utilize lead acid for example, are often unsuitable for use in high-power, low-weight applications. Other known battery technologies may be considered too unstable or hazardous for use in consumer product applications, such as portable wireless devices.
In accordance with a conventional advanced battery design, individual cells are hardwired together and to the positive and negative power terminals of the battery. Various electronic components which may be incorporated into the battery design must also be hardwired to the cells. It should be apparent to those skilled in the art that such conventional interconnection approaches provide for little, if any, flexibility when attempting to alter the series and/or parallel hardwired connections between the cells and components.
Moreover, the wiring process typically employed in the fabrication of conventional advanced batteries is generally complicated and time consuming. Of particular concern to the designers and manufacturers of conventional advanced batteries are the unintentional wiring shorts, which develop during the wiring process. These and other design defects typically result in a reduction in the performance and service life of the battery, and often represent a significant safety concern.
Other characteristics of advanced battery technologies provide additional challenges for the designers of advanced energy storage devices. For example, certain advanced cell structures are subject to cyclical changes in volume as a consequence of variations in the state of charge of the cell. The total volume of such a cell may vary as much as five to six percent during charge and discharge cycling. Such repetitive changes in the physical size of a cell significantly complicates the mechanical housing design and electrical connection strategy. The electrochemical, thermal, and mechanical characteristics of an advanced battery cell must typically be well understood and appropriately considered when designing an energy storage system suitable for use in commercial and consumer devices and systems.
However, there remains a need for an integrated solution of chips and packaging as a new concept for the power source at the chip packaging and system level. Moreover, there is a need for a system level self-powered system, which provides flexibility and reliability, and which can be manufactured easily and at a lower cost than conventional systems.